Both Campanula rapunculoides and Kalmia latifolia contain antineoplastic substances as evidenced by the activity of plant extracts against P.338 lymphocytic leukemia in mice. The active principle of C. rapunculoides is found in the leaves of the plant, and that of K. latifolia in the wood-sap. The objective of this study is to isolate and determine the structure of the two active compounds with the hope that they may be either clinically useful drugs, or be able to act as templates for further synthetic studies. Chemical fractionation will be guided either by further in vivo tests if the compounds are sufficiently active, or by following their cytotoxic effect in a suitable in vitro system if they prove to be too toxic for possible clinical use.